1. Field of the Invention
The present invention relates to a sensor used for measuring physical quantity etc., which is specifically used as a pressure sensor for converting fluid pressure into an electric signal to output to the outside.
2. Description of Related Art
Various sensors are used in measuring physical quantity etc. For instance, a pressure sensor which detects pressure and converts the pressure into an electric signal is used for measuring fluid pressure.
Such pressure sensor includes a joint clamped and fixed to a mount, a diaphragm attached to the joint by beam-welding etc., a pressure detecting element such as a strain gauge provided to the diaphragm, a circuit portion electrically connected to the pressure detecting element and a terminal for inputting and outputting the electric signal from the circuit portion, where the fluid pressure introduced to a pressure introducing port of the diaphragm is converted to strain of diaphragm, the strain being detected by the pressure detecting element. The diaphragm and the pressure detecting element are collectively referred to as a sensor module.
Conventional examples of pressure detecting sensor will be described below.
FIG. 16 shows a first conventional example of pressure sensor.
In FIG. 16, a sensor module 101 attached with a pressure detecting element 100 is provided to a joint 102. A cap-shaped housing 103 is attached to the joint 102 and a circuit portion 104 is accommodated within a space formed between the housing 103 and the joint 102.
In the first conventional example, the circuit portion 104 is composed of a printed circuit board 105 and electrical components 106 and terminal 107 respectively attached to the printed circuit board 105
The electrical components 106 are composed of IC chip and capacitor etc., which are installed on the printed circuit board 105 by soldering. The printed circuit board 105 and the pressure detecting element 100 of the sensor module 101 are electrically connected through the wiring 108 and the base 111. The terminal 107 is composed of an intermediate terminal 109 and an I/O terminal 110 connected to the intermediate terminal 109. An end of the intermediate terminal 109 is connected to the printed circuit board 105 by soldering etc.
FIG. 17 shows a second conventional example of pressure sensor.
In FIG. 17, the circuit portion 104 of the second conventional example is composed of a flexible circuit board 115, and electrical components 106 and terminal 107 respectively attached to the flexible circuit board 115.
The flexible circuit board 115 is electrically connected to the pressure detecting element 100 through the wiring 108. The terminal 107 has an end electrically connected to the flexible circuit board 115 by soldering etc and another end exposed to a connecting port 103A opening toward the outside of the housing 103.
FIG. 18 shows a third conventional example of pressure sensor.
In FIG. 18, the circuit portion 104 of the third conventional example is composed of a ceramic board 125 provided inside a housing 103, electrical components 106 and terminal 107 respectively attached to the ceramic circuit board 125.
The ceramic circuit board 125 is electrically connected to a pressure detecting element 100 through a wiring 108. The terminal 107 is composed of an intermediate terminal 109 and an I/O terminal 110 connected to the intermediate terminal 109. An end of the intermediate terminal 109 is connected to the ceramic circuit board 125 by soldering etc.
FIG. 19 and FIG. 20 show a fourth conventional example of pressure sensor.
In these figures, sensor module 101 of the fourth conventional example is attached to a joint 102 by beam welding etc. A substantially cylindrical housing 113 having partition thereinside is attached to the joint 102.
In the housing 113, a base 114 is attached to the joint 102 and a circuit board 135 is attached to the base 114. Further, a terminal 118 is attached to the base 114 through a terminal base 117.
FIG. 21 shows a fifth conventional example of pressure sensor. The fifth conventional example is disclosed in Japanese Patent Laid-Open Publication No. Hei11-237291.
In FIG. 21, a sensor module 201 of the fifth example is welded and fixed to a tapered butt weld portion 202A of the joint 202. A substantially cylindrical housing 203 is attached to a flange 202B of the joint 202 through a crimping portion 202C.
Inside the housing 203, a circuit board 205 is attached to the joint 202 through a case 204. Further, a terminal 207 is attached to the circuit board 205 through a terminal base 206. The circuit board 205 and the pressure detecting element of the sensor module 201 is electrically connected through a base 208.
In the fourth and the fifth conventional examples, the joint 102 and 202 are fixed by a screw to a mount, thereby also working as a flange as an attachment portion.
The sensor modules 101 and 201 are butted to the joints 102 and 202 to be welded.
The housings 113 and 203 are attached to the joints 102 and 202 through the crimping portions 102A and 202C.
In the pressure sensor of the above-described first conventional example, since the electrical components 106, the base 111 and the I/O terminal 110 have to be connected on the printed circuit board 105, so that the intermediate terminal 109 is required for escaping from the force applied to the I/O terminal 110.
Accordingly, in the first conventional example, the number of the components is increased to enlarge the size of the entire sensor and increasing number of connection between mutual components is required, thereby increasing production cost. Further, since such large number of connections between components is required, much cost is necessary for securing reliability of the connection process. Further, much process such as soldering is required for electrically connecting the board and the terminal, thereby increasing production cost of the pressure sensor.
In the pressure sensor of the second conventional example, since the terminal 107 is soldered to the flexible circuit board 115, production cost can be increased. Further, when the electrical components 106 and the terminal 107 are soldered to the flexible circuit board 115, the flexible circuit board 115 has to be guarded with a glass epoxy plate in order to improve rigidity thereof, thereby also increasing production cost.
In the pressure sensor of the third conventional example, since two types of terminal, i.e. the I/O terminal 110 and the intermediate terminal 109, are required as the terminal 107, the number of components are increased to enlarge the size of the entire sensor and increasing the production cost. Further, since the ceramic of high unit component price is used as the circuit board, the production cost is increased therefore.
On the other hand, the joints 102 and 202 of the pressure sensors of the fourth and the fifth conventional examples also work as the flange. In other words, the joints 102, 202 and the flange are integrally formed.
In the pressure sensor of the fourth conventional example, since the sensor module 101 is butted to the joint 102 to be welded, the bonding portion of the joint 102 is projected, thereby lengthening dimension of the entire pressure sensor.
On the other hand, in the pressure sensor of the fifth conventional example, since the sensor module 201 is welded and fixed in a manner that the sensor module 201 is buried to the tapered butt weld portion 202A of the joint 202, the problem of lengthening the dimension of the pressure sensor can be avoided. However, since the welding is conducted in an inclined direction or perpendicular direction, welding process such as alignment of weld line etc. is troublesome.
Further, in the pressure sensor of the fourth and fifth conventional examples, the circuit boards 135 and 205 and the terminals 118 and 207 are disposed on the sensor modules 101 and 201 in order to avoid enlargement of external diameter. Accordingly, the base 114 and the terminal base 117, the case 204, the base 208 and the terminal base 206 are required, thereby increasing the number of components and lengthening the entire length of the sensor.
An object of the present invention is to provide a sensor and a pressure sensor capable of reducing cost and size and improving reliability of the electrically-connected portions.
Accordingly, in the present invention, the circuit portion and the terminal of the sensor are formed by a lead frame and a resin mold is provided to a predetermined part of the lead frame.
Specifically, a sensor according to the present invention includes: a circuit portion attached with an IC die for amplifying an electric signal detected by a detecting element; and a terminal for inputting and outputting the electric signal from the circuit portion in which the circuit portion and the terminal have a lead frame formed of a metal plate, the metal plate being provided with a resin mold for electrically insulating the lead frame.
According to the present invention, since the lead frame of the circuit portion and the terminal is formed of a metal plate, the circuit portion and the terminal are electrically connected in advance. Accordingly, since it is not necessary to provide independent I/O terminal and intermediate terminal, the number of the components can be reduced, so that the reduction in production cost in accordance with component cost reduction and the size of the entire sensor can be obtained.
Further, the process for connecting the circuit portion and the terminal by soldering etc. is not required, thereby improving reliability for inexpensively connecting the component.
Further, even when a lead frame of complicated shape is used, the shape can be held by the resin mold and insulation can be securely maintained, so that the circuit portion can work appropriately.
In the above, the resin mold may preferably include a circuit-side resin mold provided to the circuit portion and a terminal-side resin mold provided to the terminal.
According to the arrangement, since the circuit portion and the terminal have the metal plate lead frame, the lead frame connecting the circuit portion and the terminal can bent in any manner and the circuit portion and the terminal can be opposed, so that the size of the entire sensor can be reduced.
The sensor may preferably have a conductive case covering the circuit portion.
According to the above arrangement, the conductive case can shield the electromagnetic wave from the outside, so that the influence such as noise on the circuit portion by the outside electromagnetic wave can be avoided.
The terminal-side resin mold may preferably penetrate the conductive case.
In the above arrangement, since the terminal is insulated against the conductive case by the terminal-side resin mold, electricity does not run from the terminal to the conductive case on account of short circuit, thereby improving reliability. Further, since independent insulation component between the terminal and the conductive case is not necessary, the number of components can be reduced.
A gasket may preferably be interposed between the conductive case and the terminal-side resin mold, and a projection may preferably be formed on a part of the terminal-side resin mold facing the gasket.
According to the above arrangement, air sealability can be obtained by sealing the space between the components with the gasket. Accordingly, invasion of dust and humidity into the conductive case can be avoided. Further, since the projection is formed on the terminal-side resin mold, the gasket can be pressed to the conductive case by the projection, thereby enhancing sealing effect.
Further, the circuit-side resin mold and the terminal-side resin mold may preferably be mutually opposed by bending the lead frame, and a positioning projection may preferably be provided to at least one of the circuit-side resin mold and the terminal-side resin mold for determining the position of the circuit-side resin mold and the terminal-side resin mold.
According to the above arrangement, when the circuit-side resin mold and the terminal-side resin mold are bent to be mounted at a predetermined position, the mutual position thereof can be defined by the positioning projections, so that the assembly work of the sensor can be simplified.
Further, at least one of the circuit portion and the terminal may preferably have a SMT (Surface Mount Technoloy) pad for attaching electrical components to the lead frame.
According to the above arrangement, protection circuit etc. can be formed by attaching the electrical components to the SMT pad of the lead frame, thereby improving function and reliability of the sensor.
Further, the lead frame may preferably have a projection abutted to the conductive case.
According to the above arrangement, since the projection works as a ground terminal, resistance against noise can be improved.
Further, a pad for attaching a wiring for connecting the detecting element and the circuit portion may preferably be provided to the lead frame of the circuit portion.
According to the above arrangement, since independent base for connecting the wiring is not necessary, the number of components can be reduced, so that the reduction in production cost in accordance with component cost reduction and entire size of the sensor is possible.
The lead frame may preferably be bent so that the pad for attaching the wiring is located closer to the detecting element relative to the other part of the lead frame.
According to the above arrangement, when the circuit portion and the detecting element are wired by wire-bonding, the length of the wiring to be bonded can be shortened. Therefore, workability can be improved, the possibility of short circuit between the wiring and the circuit portion can be reduced and the reliability of the pressure sensor against vibration can be improved.
Further, the terminal may preferably have an input terminal, an output terminal and a common terminal.
According to the above arrangement, since the I/O terminals are formed of the lead frames, the terminal can be directly soldered on a printed circuit board.
The above sensor may preferably be a pressure sensor. In other words, the sensor of the present invention may preferably be used for detecting pressure.
According to thus arranged present invention, an inexpensive small pressure sensor having high reliability for connecting the components can be provided.
Another object of the present invention is to provide a pressure sensor capable of reducing length and facilitating production thereof.
For the object, in the present invention, the joint and the flange, which are conventionally integrated are independently formed.
Specifically, in a pressure sensor according to the present invention, the detecting element is for detecting pressure, the sensor further including: a joint attached with the detecting element and having a pressure introducing port thereinside; a flange for fixing the joint to a mount; and a case for accommodating the circuit board except for a part thereof, the case being attached to the flange, the flange being disposed so that an inner wall thereof faces the detecting element, the joint and the flange being independently formed.
According to the above arrangement, the detecting element is welded while being butted to the joint and the flange is welded to the joint. Further, the circuit board is provided on the flange to construct the pressure sensor.
Since the flange is not welded in welding the joint to the detecting element, the flange does not interfere in the welding process. Accordingly, it is not necessary to conduct welding in an unnatural direction, e.g. inclined and perpendicular direction, so that alignment of weld line etc. can be easily conducted, thereby easily producing the pressure sensor.
Since the detecting element is sunk inside the flange when the flange is attached to the joint to which the detecting element is welded, the length of the pressure sensor itself can be shortened.
Since the circuit board is attached to the flange, component such as spacer and terminal base is not required in mounting the circuit board. Accordingly, the number of the components can be reduced and the steps for assembling the components can be reduced, thereby facilitating the production of the pressure sensor.
Since the lead frame of the circuit portion and the terminal is formed of a metal plate, the circuit portion and the terminal are electrically connected in advance, so that the step for connecting the circuit portion and the terminal by soldering etc. is not required, thereby simplifying the assembly process of the sensor. Further, since intermediate terminal for connecting with the circuit portion is not required on the terminal, the number of components can be reduced and the assembly process of the sensor can be further simplified and production of the pressure sensor can be facilitated.
Further, since the case is provided to the pressure sensor, dustproof effect can be obtained. Since the case is attached to the flange by welding etc., the production of pressure sensor can be further facilitated.
In the present invention, the case may preferably be electrically conductive.
According to the above arrangement, since the conductive case can shield the electromagnetic wave from the outside, the influence such as noise on the circuit board by the outside electromagnetic wave can be avoided.